Walter Harrer, an engineer, is on the night shift and returns home in the morning to find his wife lying unsconscious in the garden. She is sent to hospital were a loss of memory is observed. Dr. Bogner, a young psychiatrist, is interested in the case and tries to help Mercedes. He talks to her husband, her former lover and her friends to see if he can get some clue as to why she can't remember who she is.
She confesses that she killed Lona Logan, her rival. But Dr. Bogner isn't sure that she's telling the truth. Did she really do it or is it pure fantasy?